Conventional articles of athletic footwear may include two primary elements: an upper and a sole structure. The upper may be generally formed from a plurality of elements (e.g., textiles, foam, leather, synthetic leather) that are stitched or adhesively bonded together to form an interior void for securely and comfortably receiving a foot. The sole structure may incorporate multiple layers that are conventionally referred to as a sockliner, a midsole, and an outsole. The sockliner may be a thin, compressible member located within the void of the upper and adjacent to a plantar (i.e., lower) surface of the foot to enhance comfort. The midsole may be secured to the upper and form a middle layer of the sole structure that attenuates ground reaction forces during walking, running, or other ambulatory activities. The outsole may form a ground-contacting element of the footwear and usually may be fashioned from a durable and wear-resistant rubber material that includes texturing to impart traction.
The primary material forming many conventional midsoles may be a polymer foam, such as polyurethane or ethylvinylacetate. In some articles of footwear, the midsole may also incorporate a sealed and fluid-filled chamber that increases durability of the footwear and enhances ground reaction force attenuation of the sole structure. The fluid-filled chamber may be at least partially encapsulated within the polymer foam, as disclosed in U.S. Pat. No. 5,755,001 to Potter, et al., U.S. Pat. No. 6,837,951 to Rapaport, and U.S. Pat. No. 7,132,032 to Tawney, et al., each of which is herein incorporated by reference. In other footwear configurations, the fluid-filled chamber may substantially replace the polymer foam, as disclosed in in U.S. Pat. No. 7,086,180 to Dojan, et al., also herein incorporated by reference. In general, the fluid-filled chambers may be formed from an elastomeric polymer material that is sealed and pressurized, but may also be substantially unpressurized. In some configurations, textile or foam tensile members may be located within the chamber or reinforcing structures and may be bonded to an exterior surface of the chamber to impart shape to or retain an intended shape of the chamber.
Articles of footwear having an upper or other component with structural elements formed of threads have also been previously proposed. U.S. Pat. Nos. 7,574,818 and 7,546,698 to Meschter, each of which is herein incorporated by reference, disclose articles of footwear having an upper with thread structural elements. The thread sections may be positioned to provide structural elements that restrict stretch in directions corresponding with longitudinal axes of the thread sections.